The present disclosure relates to a battery monitor circuit, a storage apparatus, and an electronic apparatus, an electric-powered vehicle, and a power system which use power from the storage apparatus.
The application of secondary batteries such as lithium-ion batteries has rapidly expanded to a power storage apparatus that uses a new energy system such as a solar battery or a wind power generator with a secondary battery and a vehicle storage battery. In a case where many storage elements such as unit batteries (that are also referred to as electric cells or cells and will be hereinafter referred to as battery cells) are used so as to obtain high output power, a structure in which a plurality of storage modules are connected in series is employed. A storage module is formed of battery blocks each including a plurality of battery cells, for example, four battery cells connected in parallel and/or series. Many battery blocks are included in an exterior case, so that a storage module (also referred to as an assembled battery) is formed.
A structure (referred to as a battery system) in which a plurality of storage modules are connected and a common control apparatus is disposed for these storage modules has been proposed. Each of the storage modules includes a processing unit (microprocessor (MPU)), and the MPU and the control apparatus communicate with each other via a communication unit.
In a battery system, it is necessary to monitor the state of charge (SOC) of each battery cell so as to prevent the battery cell from being overcharged or overdischarged. For example, Japanese Unexamined Patent Application Publication No. 2011-030399 discloses the probability that variations in current consumption between management units (integrated circuits) for detecting the voltage of a block (storage module) will cause variations in charging state between blocks.
The number of battery cells (or parallel connections of battery cells, but hereinafter merely referred to as battery cells) in a storage module for which an integrated circuit (hereinafter referred to as a monitor Integrated Circuit (IC)) can perform voltage detection is limited. Accordingly, as illustrated in FIG. 1, a battery monitor circuit 40 including a plurality of monitor ICs (a monitor IC1 and a monitor IC2) is provided in a single storage module.
Referring to FIG. 1, ten battery cells B1 to B10 (for example lithium-ion secondary batteries) are connected in series, and form, for example, a single storage module. In a storage module, battery blocks each obtained by connecting a plurality of battery cells in parallel are used. However, for the simplification of explanation, a case in which only battery cells are used will be described.
The ten battery cells B1 to B10 are classified into two groups, a first group of the battery cells B1 to B5 connected in series and a second group of the battery cells B6 to B10 connected in series. The voltages of the battery cells B1 to B5 in the first group are detected by the monitor IC1 via paths (not illustrated), and the voltages of the battery cells B6 to B10 in the second group are detected by the monitor IC2 via paths (not illustrated). That is, since the maximum number of battery cells that can be monitored by a single monitor IC is limited, two monitor ICs, the monitor IC1 and the monitor IC2, are used.
As a power supply for the monitor IC1 and the monitor IC2, a power supply generated by the series connection of the battery cells B1 to B10 is used. That is, one power terminal (+ side) and the other power terminal (− side) of the monitor IC1 are connected to one terminal (+ side) of the series connection of the battery cells B1 to B10 and the point of connection between the battery cells B5 and B6, respectively. One power terminal (+ side) and the other power terminal (− side) of the monitor IC2 are connected to the point of connection between the battery cells B5 and B6 and the other terminal (− side) of the series connection of the battery cells B1 to B10, respectively. Each monitor IC operates with power supplied from the above-described power supply route, and performs the detection of the voltage of a battery cell and cell balance control. By connecting the point of connection between the battery cells B5 and B6 to a point of connection between the monitor IC1 and the monitor IC2, the potential of the point of connection between the monitor IC1 and the monitor IC2 can be determined.